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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/106654] [C++23] P1774 - Portable assumptions
Date: Wed, 14 Sep 2022 11:26:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106654

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #2)
> On the C++ frontend side I'd simply handle
>=20
> [[assume(expr)]]
>=20
> as if 'expr' were in a lambda -> bool with everything captured by value.

... because it seems (ick!)

void foo()
{
  int i =3D 0;
[[assume(++i =3D=3D 1)]];
  if (i !=3D 0)
    std::abort ();
}

needs to work.  We couldn't let that ++i "escape" to GENERIC/GIMPLE, even
when protected with if (.IFN_ASSUME ()) it would create ugly PHIs.=